During the manufacturing of electronic boards, an operation consisting of cleaning the residues of the substances used to improve the solder quality (referred to as solder fluxes) is necessary in order to remove the soldering flux which adheres to the printed circuits. This removal operation is referred to, in the field, as defluxing. Fluorinated hydrocarbons, and more particularly 1,1-dichloro-1-fluoroethane (known under the name HCFC 141b), are widely used in this field. An azeotropic formulation based on HCFC 141b and methanol (known in the field under the name FORANE® 141b MGX) is particularly suitable for use under hot conditions in a defluxing machine.
However, due to its action on the ozone layer, which is not zero (ozone degradation potential ODP=0.11), HCFC 141b is subject to considerable regulations which are increasingly aimed at eliminating it. Thus, the European regulation regarding substances harmful to the ozone layer (no. 2037/2000) has prohibited the use of HCFCs (hydrochloroflurocarbons) such as HCFC 141b in solvent applications since 1 Jan. 2002, except for the fields of aeronautics and aerospace, where the ban takes effect from 2009 on European territory.
Substitution solutions aimed at replacing HCFC 141b in the defluxing applications have been proposed, in particular the use of HFC (hydrofluorocarbons) and/or of HFE (hydrofluoro ethers). HFCs and HFEs have no action on the ozone layer (ODP zero or negligible with respect to the regulations in force).
Among the most well-known and most commonly used HFCs, mention may be made, for example, of 1,1,1,3,3-pentafluorobutane (365 mfc), 1,1,1,2,3,4,4,5,5,5-decafluoropentane (4310 mee), 1,1,1,2-tetrafluoroethane (134 a), pentafluoroethane (125), 1,1,1-trifluoroethane (143 a), difluoromethane (32), 1,1-difluoroethane (152 a), 1-fluoroethane (161), 1,1,1,2,3,3,3-heptafluoropropane (227 ea), 1,1,1,3,3,pentafluoropropane (245 fa), octafluoropropane (218), (perfluorobutyl)ethylene (C4H9CH═CH2), 1,1,2,2,3,4,5-heptafluorocyclopentane (C5H3F7), perfluorohexylethylene (C6F13CHCH2), tridecafluorohexane (C6F13H) and perfluoro(methylmorpholine) (PF 5052) and also their mixtures which may contribute to improving certain properties, such as non-flammability, for example.
Among the most well-known and most commonly used HFEs, mention may be made, for example, of methylheptafluoropropyl ether (C3F7OCH3), methylnonafluorobutyl ether (C4F9OCH3), ethylnonafluorobutyl ether (C4F9OC2H5) and perfluoropyran (C5F10O), and also their mixtures.
HFCs and HFEs exhibit physicochemical properties comparable to those of HCFC 141b: good thermal and chemical stability, low toxicity, low boiling point, low surface tension. However, they have proven to be ineffective in certain defluxing applications, in particular for the defluxing of electronic boards containing solder fluxes which are not normally intended to be cleaned. These fluxes are very difficult to remove and, in the field, are called “no clean” fluxes. These fluxes come from non-wash solder creams used for surfaces difficult to solder. These creams are based on complex mixtures of organic and inorganic compounds. Among these compounds, mention may be made of metal powders with a small particle size, based on tin, silver, lead, etc., binders such as, for example, rosin, solvents, surfactant resins, thixotropic agents or halogenated activators.